Screen for casting risers



Och 1948. E. T. MYSKOWSKI ET AL SCREEN FOR CASTING RISERS Filed May 21, 1945 gwve/rvbo'w EDWIN T. MYSKOWSKI HOWARD F. TAYLOR m Wu.

Patented Oct. 19, i943 UNITED 2,451,505 SCREEN FOR CASTING RISERS Edwin T. Myskowski and Howard F. Taylor, Washington, D. 0.

Application May 21, 1945, Serial No. 594,881

4 Claims. (Cl. 22-134) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) This invention relates to a method of and apparatus for casting, and more particularly to a method of and apparatus for facilitating the re moval of risers from castings.

It is sometimes the practice in casting to employ a riser in order to obtain uniform distribution of the casting material throughout the cast-- ing chamber. Where certain hard metals are used for the casting material which are difficult to out, such as some copper base alloys, or where the size or location of the riser precludes the use of power saws to remove the riser, the removal of the riser may become a very difiicult operation involving the expenditure of considerable time and the possibility of damaging the casting.

An object of this invention is to provide an effective and efflcient method of and apparatus for facilitating the removal of risers from castings.

In accordance with one embodiment of this invention, (prior to pouring the molten casting material into the mold) a perforated screen is located in the riser chamber substantially at the junction of the riser chamber and the casting chamber. After the casting material has been poured into the mold and has solidified, the cast,- ing and riser are removed from the mold. Since the perforated screen confines the area of connection between the casting and the riser to the perforations and thereby substantially reduces the area of connection between the riser and the casting, producing a plane of weakness, the riser may be readily broken off from the casting by striking it with a hammer or other suitable device.

Other objects and advantages of the present invention will be apparent from the following detailed description taken in conjunction with the drawings wherein:

Fig. 1 is a vertical sectional view of a casting mold having a perforated screen located in the riser chamber in accordance with this invention; and,

Fig. 2 is a perspective view of a suitable screen.

Referring now to the drawings and particularly to Fig. 1 thereof, wherein is illustrated a conventional sand mold, such as may be used'in the casting of metal but which is suitable for casting of other materials suchas certain glasses and plastics which are formed by casting, it will be seen that the mold comprises a lower mold section I, or drag, and an upper mold section 2,, or cope, supported thereon. A vertically extending sprue passage 3 is formed in the sand 4, which fills the mold, and this passage connects with a horizontally extending runner passage 5. The

left end of the runner passage connects to a casting chamber 6, formed in the sand and having the desired internal configuration. At the upper end of the casting chamber 6 is formed a riser chamber 1, the sides of which may be flared outwardly slightly, as shown. In order to facilitate pouring, a funnel-shaped pouring basin 8 may be located at the entrance of the sprue passage 3.

In using a mold, such as that illustrated, the molten casting material may be poured into the pouring basin 8; it then runs down the sprue passage 3, then along the runner passage 5 and enters the casting chamber 6, gradually filling the casting chamber 6 and the riser chamber I, entering the riser chamber while still in a molten condition. The weight of the molten material in the riser chamber aids in the feeding or distribution of the material throughout the casting chamber. i l 5 After the pouring operation has been complet ed, the casting material is permitted to solidify and the casting and riser are then removed from the mold. Thereafter, ordinarily it is a simple matter to remove the runner and sprue portions of the casting merely by breaking them off, since their cross-sectional size is relatively small. However, the cross-sectional size of the riser, particularly in the plane of the junction of the riser and the casting is ordinarily quite large and may be, as shown in Fig. l, the same size as the diameter of the casting chamber. Accordingly, the riser in many cases may not be readily broken off, but must be removed by sawing or chipping with a pneumatichammer. Where the casting material is difficult to cut or to chip, or as hereinbefore stated where the location of the riser is such that access to the riser with a power saw is precluded, the removal of the riser may present considerable difficulty.

In accordance with this invention, a perforated screen Ill is located in the riser chamber at the junction between the riser chamber 1 and the casting chamber 6. The material used for the screen must be, of course, one which will not be melted at the temperature of the casting operation, and which will not alloy with or fuse to the casting material. Accordingly high melting point metals or refractory or ceramic materials may be employed, or combinations of these such as a metal screen having a coating of refractory material. Where a metal screen is employed without a refractory coating, it may be desirable to coat or plate the surface of the metal with a corrosion resistant material such as tin. While the size of the perforations in the screen and the number of the perforations per square inch is not critical, suflicient open space must be provided in the screen to permit the molten material to pass readily therethrough and, at the same time, the area of connection between the riser and the casting must be sufificiently reduced to permit easy removal of the casting from the riser, by breaking the riser off the casting. In practice it has been found that if the openings comprise about 30 of the total screen area, suflicient passage is pro vided for the molten material and atthe same time the area of connection between the riser and the casting is adequately reduced to accomplish the purposes of the present invention. A screen having perforations .032 inch in diameter, and 144 such perforations per square inch has been found to provide a satisfactory balance between these two desiderata in casting manganese bronze alloys. However, with other casting materiala having different viscosities at basting temperaa w i h a e mpl yed it ma be d s abl to increase'orto decrease the size of the perforations a id/ h at ve size i he'total p f r t ar a o e er aied' are,

as s fi mes bee ound d sirable t io a iaberti lre' l. i t cen r r t e en 0, w ch ybe a roximately 14 he dia t r o the screen, to permit the molten material to seep through the screen as it cools and reaches a highly viscous state. This,- amends in prevent-- ing sagging of the screenf Where the perforated screen It is to be used in a top pouring operation, that is, where norun'ner passage is provided and the molten material is poiired through th riser chamber into the casting chamber, the provision ithe a rture in' h enter 0 h cre t l fede '1 l n Order o P vent t e eight of he ma eria in the'riser chamber-from causing the'sereen Iii to sag downwardly into the casting chamber duri e the a n op ation. v as. b e found sirablein some cases to curve the'cross portion ofthe screen upward, as shown, to provide a convex "surface in the "riser chamber. It will be ei a tt e y more e css re e r he screen upwardly asshown, the weight of the ma: terial in'theriser chamber while it will tend to f te as. s r en d w'r wa y w l also o e th periphery of the's cre en outwardly, against the d t e riser amb th reb ra n to retain the screen inipo sition. It has been found that a radius of curvature of the cross portion of the screen equivalent" to five times the radius oi the'ifiser chamber provides a satisfactory convex surface and at. the same "time. does not involve a substantial increase intl'ie area of connection betweenthe riser and the casting. Theouter peripheral portion of the screen it) maybebent' outwardly in some cases'tof'form outwardly flared sides I2 asf'clearly shown inFig. 2. The sides I2 engage the sides of the riser chamber randaid in retaining the screen in 50's: tiori irijth chamber 'whe'rea'ctual embedding f the screen or other methods of sup porting the screen at the'junction of the casting amine riser aredifiicult or impractical. ww

'Where difi'iculty'is encountered in removing the spru from the caStirig, it would fof course, be feasible toi'nsert a'screen such as described adjacent the gate to facilitate removal of the smile. Such a screen may be "employed" in addition to thescr'een employed at the baseot the riser.

In practice in the casting of metals it has been found that removal of the riser from the casting is somewhat easier if the casting is removed from the mold as soon as the temperature of the casting is below the visible heat range and the riser is broken off at that time. This-isibelieved to be due to the fact that at the lower end of the visible heat'range while the metal is then solid, it possesses relatively lower strength and resistance to breakage than when completely cooled, that is to say, it is more brittle.

While but one embodiment of this invention has been shown and described, it will be understood that many changes and modifications may be made therein without departing from the spirit or the scope of the present invention, which is limited only by the appended claims. a

The invention described herein ma be manufactured or used by or for the Government of the United States of'Ainerican for governmental purposes without the payment of any royalties t er on 9r ih s Wltefi c lm 1. In a'casting apparatus having a riser chamber and a casting chamber, a convex perforated screen interposedbetween said riser chamber and said casting chamber and. having an aperture formed in the eentral portion thereof several times larger than the; perforations in the screen and approximately one-fourth the diameter of the screen to facilitate passage of casting materiali between the riser; chamber and the casting chamber. 7

2. In a casting apparatus having a riser chamber and a casting chamber, a convex, perforated screen interposed between said casting chamber and said riser chamber, the curved portion of said screen extending into said riser chamber away from the plane of junction between the riser and casting chambers.

3. In a casting'apparatushaving a riser chamber and a casting chamber, a convex, perforated screen interposed between'said casting chamber and said riser chamber and having its periphery located substantially at the junction between said riser chamber and said casting chamber, the

curved portion of said screen extending into said riser chamber away from the casting chamber.

4;. In a casting apparatus having'a riser chame ber and a casting chamber, a convex, metallic perforated screen interposed between said casting chamberand said riser chamber, the outer peripheral portion of said. screen being bent upwardly and outwardlyso as to wedge against the innerside Off the riser chambervand aid in re-. tat-hing the screen in position on the chamber.

U EDWIN T. MYSKOWSKI.

HOWARDF. TAYLOR.

REFEEENGES. o lrED The fcl pwih file of this patent: V

UI EEEEQ IATEfi EATENTS Cameron Mar.- 9, 1943 reiere iqe ar o e in 

